Computers had been in development since the 19th century, when Charles Babbage was trying to perfect his impossibly huge, all mechanical "difference engine."
World War II accelerated the development of an electronic version when fast computing machines were needed to help solve the complex equations created by bomb targeting and the development of the atomic and hydrogen bombs.

England's top-secret Colossus, designed by a team headed by Alan Turing and used to decipher German codes, used 1,500 vacuum tubes and is considered the first all-electronic calculating machine. At the same time, a team of engineers from IBM led by Howard Aiken built the Automatic Sequence Controlled Calculator (ASCC) at Harvard, later dubbed the Mark I.

Between 1937 and 1942, John Vincent Atanasoff and Clifford Berry built their Atanasoff-Berry Computer (ABC) at Iowa State University, now considered the first all-electronic digital computer.

In 1946, what was considered the first true computer, the Pentagon-funded, vacuum tube-powered, room-sized ENIAC (Electronic Numerical Integrator and Computer) was demonstrated publicly by its inventors, John Mauchly and John Presper Eckert, in Philadelphia. But Mauchly and Eckert used – and took credit for – the basic concepts of the ABC to build ENIAC, and it would be nearly 30 years before Atanasoff-Berry would receive the patents for their work.

In 1944, Hungarian-born Princeton mathematician John von Neumann conceived stored programming, otherwise known as software. In June 1948, British researchers Tom Kilburn and Freddie Williams working at Manchester University took advantage of von Neumann's concepts and invented "The Baby," the first stored-program computer.

But perhaps the most famous of these early computers was the UNIVAC (Universal Automatic Computer), the first widely used commercial computer. The UNIVAC I was built by the Eckert-Mauchly Computer Corp., which was bought by Remington Rand just before the UNIVAC went on sale. About the size of a small garage and containing around 5000 vacuum tubes, a total of 46 machines were built and cost $1 million each. UNIVAC was first used by the U.S. Census Bureau on June 14, 1951.

In November 1952, CBS famously used a UNIVAC to correctly predict the outcome of the Eisenhower-Stevenson presidential contest on election night, but didn't release the information in fear of affecting the outcome.

Throughout the late 1940s and 1950s, the military and commercial companies, most prominently an already well-known typewriter and adding machine company called International Business Machines (IBM), continued computer development. Soon, large computers became omnipresent throughout the military and business worlds. But no one figured anyone would want a computer at home.

Personal Computing
The late 1960s and early 1970s would bring advancements helping to aid the development of the personal computer. In 1968, Stanford Research Institute researcher Douglas C. Engelbart demonstrated a computer system consisting of a keyboard, key-pad, a graphic user interface that used frames on a screen called "windows," a word processor, hypertext that allowed you to point-and-click on a word to produce another window with linked information, and a pointing device called a "mouse" that he had patented five years earlier after introducing it at a computer conference in San Francisco.

By then, Moore and Noyce's Intel had developed the first microprocessor memory chip and, by 1973, had progressed to the 8080 chip. Enough interest had been stirred in technical research labs that people started thinking about home computers.

Featured on the cover of the January 1975 issue of Popular Electronics was the first personal computer, the Altair 8800. Using the Intel 8080 chip, the Altair was invented by an ex-Air Force officer from Georgia, Ed Roberts, and manufactured by his Albuquerque, N.M., company, MITS.

Hobbyists could buy these small personal computers in kit form, but they A host of companies such as DEC, NEC, Xerox, Epson, AT&T and HP – none of which previously believed that a mainstream consumer market existed – quickly jumped on the home PC bandwagon. These machines came to be known as "clones" since they so closely resembled the technology included in the IBM PC. In late 1983, IBM itself tried to capitalize on the market it had created by releasing its IBM PCjr. The lack of innovation and its much derided "chicklet" keyboard doomed the product, however.

IBM followed up the PCjr. in 1984 with the Kaypro-like IBM transportable. A start-up company called Compaq made the first IBM-compatible portable in 1986.

Computers, however, required users to memorize a series of complex commands to operate their machines. In 1984, Apple unveiled the Lisa, which used a graphical user interface (GUI), developed originally at Xerox Corp.'s Palo Alto Research Center (PARC). Instead of a keyboard and arcane typed commands, Engelbart's mouse was used to move the cursor around the screen, now filled with icons and pull-down menus that represented programs, functions and commands, a navigation method called a graphic user interface, or GUI.

In January 1984, this so-called point-and-click technology came to the masses via the Apple Macintosh. A year later, Microsoft brought the GUI to IBM-compatible machines with the introduction of its Windows operating system. Both these operating systems introduced the concept of WYSIWYG – What You See Is What You Get – pronounced WHIZ-ee-wig. The idea was that what you saw on the screen is what your printer would produce.

After Windows and the Macintosh hit the market, the computer industry began the search for the "killer app" – a software application that would drive home computer sales. Word processing programs such as WordStar and spreadsheet programs such as Dan Bricklin's and Bob Frankston's VisiCalc (1981) slowly gave way to WordPerfect and Mitch Kapor's Lotus 1-2-3 (1983), and then to Microsoft versions, Word, also first introduced in 1983, and Excel, which now dominate the market. Another killer app, desktop publishing, was introduced with Aldus' PageMaker program in 1985, and allowed consumers to create their own sophisticated brochures, presentations and documents.

In 1990, Microsoft spent $10 million to promote Windows v3.0, considered the first version of Windows ready for prime time. In 1992, Windows was upgraded to v3.1, and Microsoft sold a million copies in the first 30 days. The next major Windows upgrade arrived three years later with Windows 95, which was backed with a $300 million ad campaign; within a year, the company had shipped 30 million copies. In 1993, Intel introduced the first Pentium processor, which contained 3.2 million transistors.

The introduction of Windows 95 jump-started an operating system war when Apple accused Microsoft of stealing the "look and feel" of the Macintosh, ironic since Macintosh had itself stolen its look-and-feel from Xerox. The war of words and lawsuits, coupled with advances in modem technologies and simple-to-use software programs, energized the PC industry as more and consumers decided they wanted a personal computer at home. The use of the personal computer and digital networks allowed people to "telecommute" – work at home as efficiently as they worked in the office. A new type of small office/home office (SoHo) sprang into being, with tens of millions of workers abandoning their daily commute to work from home. Manufacturers of office equipment began designing phone systems, fax machines and photocopiers specifically for these smaller home-based operations.

Gordon Moore's famous 1965 "law" that chip performance would double every two years proved to be conservative. Early PCs running at 4 bits doubled to 8 with the IBM-PC, then to 16-bit with the IBM PC AT (Advanced Technology), and 32-bit with the Macintosh. Current personal computers run on 64-bit, 4 GHz-plus processors.
Over the last 15 years, other computer technologies followed the precepts of Moore's law. Eight-inch floppy discs morphed into 5.25-inch floppy disks to 3.5-inch microfloppies in the late 1980s. But the need for more capacities have turned the venerable floppy disk into an anachronism and given rise to recordable CD disks and then to recordable DVD disks, and alternative high-capacity removable media technologies, such as the Iomega Zip and now to flash memory cards used in both PCs and portable devices such as MP3 players and digital cameras with capacities reaching 2 GB.

Hard drive capacity has expanded literally a million-fold. The first hard disk drive, the Ramac, was invented in the early 1950s by an IBM research team in San Jose, Calif., by a team led by Reynold B. Johnson, had 50 24-inch diameter double-sided aluminum magnetic disks, weighed a ton and stored a whopping five megabytes. Drives in early PCs stored only kilobytes, then megabytes, and now mini drives that are no larger than a quarter but can store more than a hundred gigabytes.
Printers moved from computerized typewriters to clunky dot-matrix printers requiring continuous feed sprocket-holed paper, to the introduction of the Hewlett-Packard ThinkJet, the first ink jet printer, and the HP LaserJet, the first consumer laser printer, both in 1984.

Monochrome screens slowly gave way to color screens in the mid-1980s, thanks in part to the introduction of the 256-color VGA monitor included with the IBM PS/2 line in 1987. The first flat-screen LCD panels began appearing in the late 1990s and are now the norm.

Portable Computing
In the late 1990s, a combination of advanced chip, power and screen technologies resulted in an avalanche of newer and increasingly sophisticated information and communication gadgets, not only for use at home but on the road as well.

The growth of what would become the handheld computing market was driven by the transformation of the corporate environment into an extended, virtual enterprise, supported by a mobile, geographically dispersed workforce requiring fast, easy remote access to networked resources and electronic communications. The emergence of corporate data infrastructures that easily support remote data access further encourages the growth of the handheld computing market.

The acceptance of mobile computing may have been made easier by the TV show "Star Trek". Producer Gene Roddenberry forbade pen and paper on the 23rd century U.S.S. Enterprise, giving rise to the Tricorder and the concept of mobile information devices. In the 1970s, for instance, Xerox's PARC research center explored the Dynabook notebook computer concept.

But the first mobile information device in the real world was the Osborne 1 portable computer in June 1981, followed in July 1982 by the first Compaq and the Kaypro 2 in October 1982. All three "luggable" computers were the size of small suitcases and each weighed about 25 pounds; the Kaypro was mockingly nick-named "Darth Vader's Lunchbox."

But these portable computers – which proved to be less than handy – and their successors, laptops and then notebook computers, merely served as replacements for their full-sized counterparts.

Consumers were seeking a new type of device, one that didn't replace a computer, but supplemented it, something to replace their paper-based appointment calendars and address books. Sharp obliged in 1988 with the introduction of the Sharp Wizard, this featured a small LCD screen and a tiny QWERTY keyboard.
Faster and more functional chips led in 1993 to the morphing of the electronic organizer into the personal digital assistant (PDA), a term coined by Apple CEO John Sculley. The first true PDA was the Apple Newton, the first organizer to include a touch screen and handwriting recognition software. Several other companies soon announced similar portable computing devices.

In April 1996, a small company called Palm Computing took the idea of the Newton, shrunk it, made it more functional, improved the handwriting recognition and halved Newton's price to produce the first modern PDA, the Palm Pilot.

Microsoft followed in September 1996 with its own PDA operating system, Windows CE, and then, in April 2000, the PocketPC operating system, which has been licensed to PDA makers including Casio, Sharp, Hewlett-Packard Co. and Compaq Computer Corp. The initial touch screen PDAs used monochrome displays, but by 2000, nearly all Palm and PocketPC PDAs had color screens.

Current high-end PDAs pack in Wi-Fi wireless Internet and Bluetooth wireless synchronization technology, and many now include built-in digital cameras and digital music and video playback capabilities. Palm is still the dominant format along with Microsoft's Windows Mobile OS.